1. Field of the Invention
This invention relates to power supplies, and more particularly relates to implementing a low cost multiple output redundant power supply.
2. Description of the Related Art
A power supply, sometimes known as a power supply unit or PSU, is a device or system that supplies electrical or other types of energy to an output load or group of loads. A power supply, in some embodiments may be configured to convert power in one form to another form, such as converting AC power to DC power. The regulation of power supplies is typically done by incorporating circuitry to tightly control the output voltage and/or current of the power supply to a specific value. The specific value is closely maintained despite variations in the load presented to the power supply's output, or any reasonable voltage variation at the power supply's input.
For example, in an electrical device such as a computer, the power supply is typically designed to convert an AC voltage input such as is traditionally provided by a conventional wall socket, into several low-voltage DC power outputs for transmission to the internal components of the computer. Conversion is typically performed in stages that may include various different stages such as a rectification stage, an active filter stage, a regulator stage, etc. The various stages may be a boost, a buck, or other derivative topology. In one embodiment of a conventional power supply, a regulator stage may be implemented to provide a number of different voltages to a computer system via a bus. For example, the power supply may include a regulator stage that regulates voltages on the bus of +12 volts, +5 volts, +3.3 volts, and −12 volts. These regulated voltages are then provided to the computer system which uses the different voltages to power the various electrical sub-systems of the computer system.
For high availability systems, often two or more redundant systems are provided so that a single failure will not cause the system to be unavailable. The high availability system may have two distinct systems or may include two or more sub-systems. In either case, the systems require regulated power at various voltages. One solution to provide power is to provide two or more separate power supplies. This solution has an advantage of being very reliable, since if any one power supply fails, the other can pick up the load of the failed power supply. However, in normal operation each power supply provides power only up to 50% of the load. As more power supplies are added, the amount of power provided by each power supply is further reduced. Typically, power supplies operate most efficiently near full load and efficiency degrades rapidly below around 50%. Providing two fully redundant power supplies where each is usually operating below 50% is inefficient. In addition, providing two separate power supplies is relatively expensive compared to a single power supply.
Another solution is a single power supply that provides power to multiple systems. In such an implementation, efficiency is usually high because the single power supply typically operates closer to full load. However, reliability is low because a single failure in the single power supply will make power to the systems unavailable. The single power supply solution is less expensive than providing two power supplies.
Thus, there is a need for a low cost multiple output power supply that can efficiently provide power to two or more systems while providing protection for those systems in the event of a regulator stage component failure.